<!DOCTYPE html>
<html lang="zh">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="nav_demo.css">
    <title>Nav Demo</title>
    <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self'; style-src 'self';">
</head>

<body>
    <hr>
    <nav>
        <a href="#" id="home">首页</a>
        <a href="#" id="about">关于</a>
        <a href="#" id="service">服务</a>
        <a href="#" id="contact">联系</a>
    </nav>
</body>
<script src="nav_demo.js"></script>

</html>